What motivates people? How do they get what they want? Economist Steven Levitt sets out to explore such questions, along with some of life's riddles, in Freakonomics, co-authored by Stephen J. Dubner.

A professor at the University of Chicago, Mr. Levitt uses statistics to examine matters of everyday life: His subjects range from abortion and crime to game shows. Some of the chapter titles from Freakonomics illustrate Levitt's wide-ranging curiosity: "Why Do Drug Dealers Still Live with Their Moms?" and "How Is the Ku Klux Klan Like a Group of Real-Estate Agents?" are two. Levitt talks about his ideas with Scott Simon.